Fuel pump

ABSTRACT

The invention contemplates an improved diaphragm-operated fuelpump construction having particular use with a multiple-cylinder two-cycle engine, wherein two phased-displaced series of fluidpressure pulses are used for diaphragm actuation. In the primary pumping chamber, inlet and outlet check valves assure the desired single direction of fuel flow, and strikingly enhanced performance results from novel employment of an additional diaphragm-operated chamber, on the inlet side of the inlet check valve, said inlet-chamber diaphragm being driven by fluidpressure pulses which are phase-displaced from those which actuate the diaphragm of the primary pumping chamber. In the form specifically disclosed, a third diaphragm-operated chamber is on the outlet side of the outlet check valve, and the inlet and outlet chamber diaphragms are driven in phase with each other and, therefore, in phase-displaced relation with drive of the primary pumping-chamber diaphragm.

Unite States Patent [191 Hundertmark FUEL PUMP [75] Inventor: James M. Hundertmark, Fond du Lac, Wis.

[73] Assignee: Brunswick Corporation, Skokie, Ill. [22] Filed: Nov. 19, 1 973 [21] Appl. No.: 416,832

[44] Published under the Trial Voluntary Protest Program on January 28, 1975 as document no.

[52] US. Cl. 417/395 [51] Int. Cl. F04B 43/06 [58] Field of Search 417/395, 389, 383, 384

[56] References Cited I UNITED STATES PATENTS 2,713,858 7/1955 Armstrong et a1, 417/395 X 3,424,091 l/l969 Turner 417/395 3,556,687 l/1971 OConnor 417/395 Primary Examiner-William L. Freeh Assistant Examiner-Richard Sher Attorney, Agent, or FirmHopgood, Calimafde, Kalil, Blaustein & Lieberman [57] ABSTRACT The invention contemplates an improved diaphragmoperated fuel-pump construction having particular use with a multiple-cylinder two-cycle engine, wherein two phased-displaced series of fluid-pressure pulses are used for diaphragm actuation. In the primary pumping chamber, inlet and outlet check valves assure 7 Claims, 5 Drawing Figures 9 wow/=05 was l b 455B n FUEL PUMP This invention relates generally to pumps and more specifically to an improved diaphragm-operated fuel pump for intemal-combustion engines of the two-cycle variety, as used, for example, in certain outboard motors, chainsaw motors, and the like.

One of the requirements of a, diaphragm-operated pump of the character indicated is that it produce a substantially continuous flow at substantially constant delivery pressure, and US. Pat. No. 2,835,239 describes a particular construction intended to achieve this result, using two diaphragm chambers driven by fluid-pressure pulsations taken from adjacent crankcase chambers of a two-cylinder two-cycle engine; one of these diaphragm chambers is driven by pulsations from one crankcase chamber for direct pump action and is characterized by inlet and outlet check valves, while the other diaphragm chamber is driven by pulsations from the other crankcase chamber and is on the outlet side of the outlet check valve. This kind of construction has proved satisfactory for many applications, but it has been found to have limitations, particularly when high performance is desired. It is believed that the performance difficulty stems from an inadequate seating of the inlet check valve under high-speed conditions.

It is, accordingly, an object of the invention to provide an improved fluid pump of the character indicated.

Another object is to provide such a pump which will avoid the above-noted problem under conditions of a highperformance demand.

A specific object is to achieve the above objects with a construction providing increased output for a given diaphragm area in the primary pumping chamber.

A general object is to provide such a pump at little or no additional cost or complexity, and lending itself to essentially the same ready inspection and servicing that characterize present constructions.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification, in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, a preferred form of the invention:

FIG. 1 is a simplified vertical sectional view through a fuel pump of the invention, with a schematic showing of operating connections;

FIG. 2 is a bottom view of the body-casting assembly of the pump of FIG. 1;

FIG. 3 is a plan view of enregistered diaphragm and gasket parts of the pump of FIG. 1;

FIG. 4 is a plan view of the head casting used in the pump of FIG. 1; and

FIG. 5 is a simplified graphical plot to illustrate improved performance achieved by use of the invention.

Referring to FIGS. 1 to 4, the invention is shown in application to a fuel pump for a multiple-cylinder two cycle engine 10, using inlet fuel drawn in line 11 from a fuel tank and delivering fuel under pressure into line 12 to the engine carburetor. The pump comprises a body casting having three chambers 14-15-16 each of which is closed along its lower side by diaphragm means which is preferably a single piece of flexible material such as Neoprene sheet but which for purposes of better identification is marked with separate numbers 17-18-19, since it serves a separate diaphragm function for operation at each of the respective chambers 14-15-16. Also, for better identification, the chambers 14-15-16 will be sometimes referred to as diaphragmoperated chambers. The diaphragm means is clamped between the body casting 13 and a head casting 20, with suitable upper and lower gaskets 21-22 to assure a diaphragm seal to each of the chambers 14-15-16 and to the respective fluid-pressure operating cavities 23-24-25 in head beneath chambers 14-15-16.

From FIG. 4, it will be seen that cavities 23-25 are interconnected by passage means 26 communicating with a single control port 27 and that cavity 24 has its own independent control port 28; the interconnection 26 is only schematically shown in FIG. 1, but the respective control ports 27-23 will be understood to be connected as by flexible conduits 29-30 to separate crankcase chambers of engine 10. Connections 29-30 are identified by legends Phase A and Phase B, respectively, to denote the phase-displaced nature of fluid-pressure pulsations derived from the two crankcase-chamber connections to engine 11 Inlet and outlet check-valve subassernblies 31-32 are removably secured by clamp means 33 to the upper wall of the main or pumping diaphragm-operated chamber 15, the unidirectional flow function of these valves being shown by heavy arrows in FIG. 1. Outlet valve 32 discharges into an upper chamber 34 having an inside-ported connection 35 to the diaphragmoperated chamber 16, from which an outlet fitting 36 furnishes a flow of fuel under pressure to the carburetor-supply or outlet-fuel line 12.

On the inlet side of the pump, a cap 37 is removably secured (by means 38) over ports 39-4@ to the respective diaphragm operated chambers 14-15, thus defining a connecting chamber within which fuel-strainer means 41 may function. As shown, strainer means 41 is a frusto-conical wire-mesh basket clamped and peripherally sealed by an O-ring gasket 42 and by the skirt of cap 37; a supply formation 43 integral with cap 37 enables servicing of means 41 without detachment of the conduit connection 11, as will be understood.

Because of the integrated nature of the construction in FIG. 1, it has not been possible to describe what is new without also describing what has been past practice. Briefly, however, it may be noted that except for the inlet diaphragm-operated chamber 14 and its associated means and connections 17-23-34, the described device represents the practice of the recent past. Such practice has thus relied upon two diaphragm-operated chambers 15-16, (a) wherein chamber 15 is the main or pumping chamber, served by inlet and outlet check valves 31-32, (b) wherein the two applicable diaphragm areas 18-19 are fluid-pressure operated in opposed phase relation, and (c) wherein cap 38 and strainer means 41 are serially connected only to line 11 and to chamber 15, via check valve 31. As noted above, such a construction has been found to impose undesirable limitations when there is a demand for high performance, and it is believed that such limitations are attributable to an incomplete or unreliable seating of the inlet check valve 31 during the blocking phase of its cycle. With the additional diaphragm-operated inlet chamber 14 of the invention, it is believed that this difficulty is overcome or materially reduced, by reason of the ability of inlet diaphragm 17 to create a transient reduced pressure (in chamber 14 and within cap 37), whenever the inlet valve 31 must be seated; thus, the

additional diaphragm action at 17, in phase-displaced relation with the action at 18 induces a greater pressure differential across valve 31, for its more effective closure. This enhanced effectiveness is realized in spite of the inertial effects attributable to the fuel under highspeed (high-flow) conditions.

The invention will be better understood from a description of its operation, commencing with the dry condition wherein all the fuel is in the tank, and on the assumption that Phases A and B are l80-displaced, in terms of the operating cycle of the engine shaft, suggested at in FIG. 1. Under such conditions, starterrotation of the engine 10 drives the inlet and pumping diaphragms 17-18 in phase opposition, i.e., one of these diaphragms moves in one direction while the other moves in the opposite direction. Before fuel arrives at cap 37, a downward movement of the inlet diaphragm 17 helps to force closure of the inlet check valve 31 and to induce a vacuum in cap 37, causing fuel to be drawn into line 11. In the upward-movement part of the cycle of inlet diaphragm 17, the pumping diaphragm 18 is in its downward-movement phase, and, since the effective area of diaphragm 17 is less than that of diaphragm 18, valve 31 not only opens promptly but the chamber of cap 37 is still subjected to a net negative pressure (partial vacuum), so that fuel continues to be drawn into line 11. Fuel is not forced back down the fuel line because any tendency of pressure rise in chamber 14 is well dissipated by the vacuum induced in the pumping chamber 15. Thus, as long as shaft 10 rotates, a vacuum is induced in line 11, even during the half cycles in which valve 31 is closed. The inlet diaphragm 17 thus provides for more effective lift of the fuel, before and after it reaches the chamber of cap 37, and for increased seating efficacy of valve 31 once the fuel has reached the pump. Thus, once fuel reaches the pump, there is a substantially reduced possibility of fuel passage backward through valve 31, and the improved seating of valve 31 develops increased delivery pressure and flow rate delivered by a given size pump. At least part of the enhanced capacity of the pump can be attributed to the pumping action at inlet diaphragm 17, in that whatever diaphragm 17 pumps is naturally accepted by the main diaphragm-operated chamber 15.

FIG. 5 is provided as an illustration of the magnitude of improvement realized by the invention, for diaphragm-area proportions substantially as shown in the drawing, i.e., wherein the effective area of each of the inlet and outlet diaphragms 17-19 is approximately one half that of the main diaphragm 18. The preferred area relationship has not yet been determined, but certainly it can be said that the effective area of the inlet diaphragm 17 is preferably less than that of the main diaphragm 18, in order that the fuelvolume pumped at 17 can be assuredly drawn into chamber during the same part of the cycle.

FIG. 5 depicts fuel flow and delivery pressure observed for a pump of the invention (designated as a three-chamber pump), in comparison with fuel flow and delivery pressure achieved by parallel use of two conventional two-chamber pumps. Each of the twochamber pumps was as herein acknowledged and described as present commercial devices, each having a pumping diaphragm area to match that of the single three-chamber pump of the invention, and the area of each of the outlet diaphragms was the same, being substantially one half that of the pumping diaphragm. As seen from FIG. 5, the three-chamber pump of the invention delivered at almost the combined flow rate of the two parallel two-chamber pumps, for the slowerspeed range (1500 to 3200 r.p.m.); but for higher speeds, the single inventive pump far outperformed the combined capabilities of the two conventional pumps.* Throughout the same speed range, delivered pressure from the three-chamber pump of the invention is at all times slightly better than that from the two conventional pumps in parallel.

Flow rate is not given beyond I lbs/hr. for the inventive pump, because the flow-metering equipment had reached its limit.

The described pump of the invention will be seen to have met all stated objects of the invention. The principle of operation has been found to apply for excitationphase displacements other than 180, as for example the 120 displacement between instantaneous pressures in certain crankcases of a six-cylinder engine, or in the case of a four-cylinder two-cycle engine. Also, the increased efficacy of the pump means that mounting location is not critical, and therefore the mounting can be remote from the engine per se, thus avoiding any possibility of vapor lock due to engine heat.

While the invention has been described in detail for the preferred form shown, it will be understood that modifications may be made without departure from the claimed invention. For example, the pump action happened to conveniently utilize crankcase pressure changes, but in other pumping environments other. suitably phase-displaced, sources of driving-pressure pulsations may be used with equal effectiveness. Also. for example, the invention may under certain circumstances be practiced without reliance on the third or outlet diaphragm 19, should efficient liquid-drawing be the primary objective.

What is claimed is:

1. A fuel pump for supplying fuel from a fuel source to the carburetor of a two-cycle internal-combustion engine having a plurality of cylinders, comprising first and second and third chambers, pressure-responsive diaphragm means extending across each of said chambers, a fuel-supply chamber having a fuel-source connection and having overlapping connection with said first and second chambers, an inlet check valve at the connection between said fuel-supply chamber and said second chamber, means including an outlet check valve connecting said second and third chambers, said third chamber including a fuel-output connection, first crankcase-connection means on the opposite side of the diaphragm at said first chamber for a first phase of pulsed operation thereof in accordance with a firstphase, second crankcase-connection means on the opposite side of the diaphragm at said second chamber for pulsed operation thereof in accordance with a second phase in phase-displaced relation to said first phase, and third crankcase-connection means on the opposite side of the diaphragm at said third chamber for pulsed operation thereof in phase-displaced relation with said second phase.

2. The pump of claim 1, in which said first and third crankcase-connection means are connected to each other.

3. The pump of claim I, in which the effective diaphragm area of said first chamber is less than that of said second chamber.

4. The pump of claim 3, in which the first-chamber diaphragm area is in the order of one half the secondchamber diaphragm area.

5. A fuel pump for supplying fuel from a fuel source to the fuel inlet of an internal-combustion engine having an output shaft and shaft-connected means for generating in separate outlets first and second fluid-pressure pulse trains in phase-displaced relation and synchronous with shaft rotation, said pump comprising first and second chambers with pressure-responsive diaphragm means extending across each of said chambers, means including a fuel-supply chamber interconnecting said first and second chambers, an inlet check valve at the connection between said fuel-supply chamber and said second chamber, means including an outlet check valve connected to said second chamber and having means for supplying the output of said outlet check valve to the fuel inlet of the engine, first connection means on the opposite side of the diaphragm at said first chamber for connection to the first pulsed fluid-pressure outlet of such an associated intemalcombustion engine, and second connection means on the opposite side of the diaphragm at said second chamber for connection to the second pulsed fluidpressure outlet of the engine, whereby said inlet check valve is subjected to the push-pull differential-pressure fluctuation generated by phase-displaced excitation of the respective diaphragms at said first and second chambers.

6. The pump of claim 5, in which said fuel-supply chamber includes strainer means separating the space within said chamber into an unstrained-fuel inlet volume and a strained-fuel outlet volume, said strainedfuel outlet volume communicating directly with both said inlet check valve and said first-mentioned chamber, whereby both said first and second diaphragmoperated chambers operate only upon fuel which has passed said strainer means.

7. A pump for supplying fluid from a fluid source to a fluid-delivery outlet, cyclically operative means for developing separate pulsed-cycle outputs in constant phase-displaced relation, said pump comprising first and second chambers with flexible diaphragm means extending across each of said chambers, means including a fluidsupply chamber interconnecting said first and second chambers, an inlet check valve at the connection between said fluid-supply chamber and said second chamber, means including an outlet check valve connected to said second chamber and having means for supplying the output of said outlet check valve to said fluid-delivery outlet, first connection means on the opposite side of the diaphragm at said first chamber for operative connection to one of said pulsed-cycle outputs of said cyclically operative means, and second connection means on the opposite side of the diaphragm at said second chamber for operative connection to the other of said pulsed-cycle outputs of said cyclically operative means, whereby said inlet check valve is subjected to the push-pull differential-pressure fluctuation generated by phase-displaced excitation of the respective diaphragms at said first and second chambers.

Page 1 of 2 UNITED STATES PATENT OFFICE EETEFICATE OF CORRECTION f PATENT N0. 4,975

DATED 1 December 9, 1975 INVENTOR(S) James Hundertmark It is certified that error appears in the above-identified patent and that said Letters Patent l are hereby corrected as shown below:

Cancel the sheet of drawing containing Figures 1 and 5 and substitute the attached sheet of drawing.

Signed and Sealed this eighteenth Day of May 1976 [SEAL] A nest:

RUITH C. M A SON C. MARSHALL DANN Arresting ()j/iccr (ummissimwr uj'lau'nls and Trademarks 

1. A fuel pump for supplying fuel from a fuel source to the carburetor of a two-cycle internal-combustion engine having a plurality of cylinders, comprising first and second and third chambers, pressure-responsive diaphragm means extending across each of said chambers, a fuel-supply chamber having a fuel-source connection and having overlapping connection with said first and second chambers, an inlet check valve at the connection between said fuel-supply chamber and said second chamber, means including an outlet check valve connecting said second and third chambers, said third chamber including a fuel-output connection, first crankcase-connection means on the opposite side of the diaphragm at said first chamber for a first phase of pulsed operation thereof in accordance with a first-phase, second crankcaseconnection means on the opposite side of the diaphragm at said second chamber for pulsed operation thereof in accordance with a second phase in phase-displaced relation to said first phase, and third crankcase-connection means on the opposite side of the diaphragm at said third chamber for pulsed operation thereof in phase-displaced relation with said second phase.
 2. The pump of claim 1, in which said first and third crankcase-connection means are connected to each other.
 3. The pump of claim 1, in which the effective diaphragm area of said first chamber is less than that of said second chamber.
 4. The pump of claim 3, in which the first-chamber diaphragm area is in the order of one half the second-chamber diaphragm area.
 5. A fuel pump for supplying fuel from a fuel source to the fuel inlet of an internal-combustion engine having an output shaft and shaft-connected means for generating in separate outlets first and second fluid-pressure pulse trains in phase-displaced relation and synchronous with shaft rotation, said pump comprising first and second chambers with pressure-responsive diaphragm means extending across each of said chambers, means including a fuel-supply chamber interconnecting said first and second chambers, an inlet check valve at the connection between said fuel-supply chamber and said secOnd chamber, means including an outlet check valve connected to said second chamber and having means for supplying the output of said outlet check valve to the fuel inlet of the engine, first connection means on the opposite side of the diaphragm at said first chamber for connection to the first pulsed fluid-pressure outlet of such an associated internal-combustion engine, and second connection means on the opposite side of the diaphragm at said second chamber for connection to the second pulsed fluid-pressure outlet of the engine, whereby said inlet check valve is subjected to the push-pull differential-pressure fluctuation generated by phase-displaced excitation of the respective diaphragms at said first and second chambers.
 6. The pump of claim 5, in which said fuel-supply chamber includes strainer means separating the space within said chamber into an unstrained-fuel inlet volume and a strained-fuel outlet volume, said strained-fuel outlet volume communicating directly with both said inlet check valve and said first-mentioned chamber, whereby both said first and second diaphragm-operated chambers operate only upon fuel which has passed said strainer means.
 7. A pump for supplying fluid from a fluid source to a fluid-delivery outlet, cyclically operative means for developing separate pulsed-cycle outputs in constant phase-displaced relation, said pump comprising first and second chambers with flexible diaphragm means extending across each of said chambers, means including a fluidsupply chamber interconnecting said first and second chambers, an inlet check valve at the connection between said fluid-supply chamber and said second chamber, means including an outlet check valve connected to said second chamber and having means for supplying the output of said outlet check valve to said fluid-delivery outlet, first connection means on the opposite side of the diaphragm at said first chamber for operative connection to one of said pulsed-cycle outputs of said cyclically operative means, and second connection means on the opposite side of the diaphragm at said second chamber for operative connection to the other of said pulsed-cycle outputs of said cyclically operative means, whereby said inlet check valve is subjected to the push-pull differential-pressure fluctuation generated by phase-displaced excitation of the respective diaphragms at said first and second chambers. 